Study of energy transfer between rare earth ions in CaS host by photoluminescence spectra

When CaS:Sm3+, Eu2+ is excited at 476.5nm (Ar+), the emission spectra taken at room temperature and at 77K are different, indicating that there are two competitive energy transfer processes__Sm3+" border=0 src="/.dejavu/.tact/lib1/art410/pcdata/html_gif/charset.gif/bam.gif"Eu2+ and Eu2+" border=0 src="/.dejavu/.tact/lib-1/art410/pcdata/html_gif/charset.gif/bam.gif"Sm3+ with phonon participation. So, the luminescence intensity of Sm3+ increases first, and then decreases as the concentration of Eu2+ is increasing.